package com.buddy.leetcode._10;

import java.util.ArrayList;
import java.util.List;

/**
 * 给定一个仅包含数字 2-9 的字符串，返回所有它能表示的字母组合。
 * 给出数字到字母的映射与电话按键相同。注意 1 不对应任何字母。
 * 示例:
 *      输入："23"
 *      输出：["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"].
 * 说明:
 * 尽管上面的答案是按字典序排列的，但是你可以任意选择答案输出的顺序。
 */
public class CombinePhoneNumber {
    private List<String> res;

    public static List<String> letterCombinations(String digits) {
        List<String> res = new ArrayList<String>();
        if (digits.isEmpty()) return res;
        String[] dict = new String[]{"abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"};
        return letterCombinationsDFS(digits, dict, 0, "", res);
    }

    private static List<String> letterCombinationsDFS(
            String digits, String[] dict, int level, String out, List<String> res) {
        if (level == digits.length()){
            res.add(out);
            return res;
        }else {
            String str = dict[digits.charAt(level)-'2'];
            for (int i = 0; i < str.length(); ++i) {
                out += str.charAt(i);
                res = letterCombinationsDFS(digits, dict, level + 1, out, res);
                out = out.substring(0,out.length()-1);
            }
        }
        return res;
    }

    public static List<String> myLetterCombinations(String digits) {
        List<String> res = new ArrayList<String>();
        if (digits.isEmpty()) return res;
        List<String> tempList = new ArrayList<String>();
        res.add("");
        String[] dict = new String[]{"abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"};
        for (int i=0;i<digits.length();++i){
            String str = dict[digits.charAt(i)-'0'-2];
            for (int j = 0;j<res.size();++j){
                String temp = res.get(j);
                for (int k = 0;k<str.length();++k){
                    tempList.add(temp+str.charAt(k));
                }
            }
            res.clear();
            res.addAll(tempList);
            tempList.clear();
        }
        return res;
    }

    public static void main(String[] args){
        System.out.println(letterCombinations("23"));
    }
}
